Second stage cooling

Report
Progress in deep laser cooling of Strontium at
VNIIFTRI
State Scientific Center
of the Russian Federation
National Research Institute for
Physical-Technical and Radio Engineering
Measurements
S. Strelkin, A. Galyshev, O. Berdasov,
A. Gribov, S. Slyusarev
P.N. Lebedev
Physical Institute of
the Russian Academy
of Science
K. Khabarova, N. Kolachevsky
GLONASS Accuracy
m
50
50.0
Anticipated (in 2002)
Obtained
Anticipated (in 2008)
8 years ago
GLONASS
allowed one to
choose the
appropriate street
from the list…
45
40
35
35.0
30.0
30
25
20.0
20
3 years ago one
knew exactly what
the street it was.
16.5
15
12.4
12.8
10.0
8.2
7.0
10
5
8.0
5.5
6.5
5.0
2.8
2.5
0
2006
2007
2008
2009
2010
2011
GLONASS accuracy has significantly improved over last
five years
Frequency standard’s evolution
1D optical lattice and magic wave lengths
M. Takamoto et al., PRL 102, 063002 (2009)
Sr-87 optical lattice clock instability
“An optical lattice clock with accuracy and stability at the 10 -18 level”, B.J.Bloom etc., Nature, vol 506, 6 Feb. 2014
Sr-87 optical lattice clock in Russia
2010 – Sr lattice clock project within GLONASS
program has been started at VNIIFTRI
2011 – collaboration with P.N. Lebedev Physical
Institute
Sr electronic level diagram
Sr isotopes: 88 (81%), 87 (7%), 86 (10%), 84 (2%)
Clock transition:
1S
3P
0
0
Natural linewidth = 1 mHz
(allowed by hyperfine
coupling of 3P0 to 3P1 and
1P ) @ 698 nm
1
Weak sensitivity to the
magnetic field
(J = 0 →J = 0 transition)
3D scatch of the vacuum system
Sr source
Zeeman slower
Trap
Vertical set method of the system
Optical scheme
oven
MOT beams
camera
Zeeman slower
PMT
Silver
mirror
detection
beam
Zeeman slower
beam
First stage cooling
~106
Without repumpers
~4x107
With repumpers
количество
atoms number
атомов, [10 8]
Repumping effect on trapped atoms number
с лазерами
перекачки
0.4
2=360 ms
мс
0.2
0.0
-2.0
1=24 ms
без лазеров
перекачки
-1.5
-1.0
-0.5
0.0
time, [s]
время
tс, []
x10 more atoms with repumpers
Temperature and number of atoms in the 1st MOT
1 cm
Number of atoms in the “blue” MOT N~4*107
Т ~ 3 мК (depends on the intensity)
Second stage cooling
Narrower transition 1S0 3P1
is well-suited to Doppler
cooling
(@689 nm, natural linewidth
7,5 kHz, Doppler limit 200 nK)
Narrow line requires narrow laser
spectrum and high frequency stability
Narrowing of the red MOT cooling laser
Toptica DL pro laser
system @689 nm
ULE systems manufacturing and
transportation
The distance
covered during
transportation 60 km
Laser stabilization
fast
LD
G
slow SERVO
modulation 20 MHz
AOM
AOM
PD
EOM
wavemeter
PD
l/4
Beatnotes
ULE-1
Linear drift ~300 mHz/s
SERVO
PD
ECDL @689
Toptica DL-100 (DL-1)
beatnote
DL-1/DL-2
ECDL @689
Toptica DL-pro (DL-2)
Frequency comb
H-maser
Allan deviation
SERVO
äåâèàöèÿ Àëëàí à (í î ðì èðî âàí í àÿ)
ULE-2
êðèâàÿ 1
PD
beatnote
-13
-13
DL-1/frequency
comb
10
10
êðèâàÿ 2
linear drift
subtracted
-14
-14
10
10
11
10
10
100
100
âðåì ÿ óñðåäí åítime
èÿ [c] [s]
averaging
1000
1000
ULE-1 and ULE-2 Critical Temperatures
0
beatnote frequency DL-1/DL-2, MHZ
temperture ULE-2, C
14
12
10
16
18
20
22
28
26
24
100
ULE-1 spacer:
ATF films
Finesse 60 000
80
60
40
ULE-2
Тс
0
= 27 С
ULE-2 spacer:
Lebedev
Physics Institute
20
0
ULE-1
0
8
Тс
= 12 С
10
12
14
Finesse 45 000
16
0
temperature ULE-1, C
Beatnote spectral linewidth
power spectral density [a.u.]
0.16
0.14
0.12
0.10
FWHM=110 Hz
0.08
0.06
0.04
0.02
0.00
-3000
-2000
-1000
0
time [s]
1000
2000
3000
Second stage cooling features
Doppler width of 1S0-3P1 transition @3 mK ~ 2 MHz
Stabilized laser spectrum
Doppler line profile
f
f0
frequency, [arb.u.]
Broadband second stage cooling
FM of cooling radiation allows to deal with different velocity
groups within Doppler profile
лазера
спектр
spectrum
laser
доплеровский
линии
контур line
profile
Doppler
f
f0
ед.]
[отн.
частота,
[arb.u.]
frequency
f (t )  f 0  f   cos[2 f mt ] ,
Broadband second stage cooling
1 mm
~106
Broadband second stage cooling
Retrapping efficiency: 8-10%
Temperature in the end of
broadband cooling: T~35 mK
Retrapping efficiency
High intensity in the first stage cooling
leads to low retrapping efficiency
коэффициент перезахвата 
0.09
BUT
0.08
0.07
0.06
0.05
0.04
0.03
0.05
0.10
0.15
0.20
I/Isat
0.25
0.30
Number of atoms in secondary MOT
Retrapping efficiency
The number of atoms in the first
MOT depends on the cooling
light intensity
Single mode second stage
Stabilized laser spectrum
Doppler line profile
after broadband cooling
Atomic cloud in the
end of the second
stage cooling
f=100 g
f
f0
T=2
mK
frequency, [arb.u.]
N=105
Clock laser systems
Clock laser systems
0.10
0.08
signal,
сигнал,V[В]
0.06
0.04
Mode TEM00
time response 21,7 ms
0.02
0.00
-0.02
-0.04
0
50
100
150
200
time, ms
Target instability 1*10-15
Finesse: 260 000
Achievable laser linewidth: ~1 Hz
Conclusions
• First stage cooling of 88Sr and 87Sr
• Two ULE stabilized lasers for second stage cooling are
assembled and characterized
• Second stage cooling of 88Sr
• Two ULE stabilized laser systems for clock transition
spectroscopy are assembled
Outlook
• Loading cooled atoms in the optical lattice at 813 nm and at 390
nm
• OPTICAL LATTICE CLOCK
Working group at VNIIFTRI
Спасибо за внимание!

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